Improvement in the manufacture of sheet-iron



UNTTED STATES PATENT OEETeE.

CHARLES H. PERKINS, OF PROVIDENCE, RHODE ISLAND.

IMPROVEMENT IN THE MANUFACTURE OF SHEET-IRON.

Specification forming part of Letters Patent No. 53,476, dated March 27,1866.

To all whom it may concern Be it known that I, CHARLES H. PERKINS, ofthe city and county of Providence, in the State of Rhode Island, haveinvented a new and Improved Process for Treating Sheet-Iron Plates thatare intended to be coated with zinc in the process for making so-calledgalvanized iron, or which are to be finished in imitation of Russiairon, of which the following is a specification.

The great difficulty which has been experionced in all attempts tomanufacture either galvanized or Russia iron plates from commonsheet-iron is the presence of the scale, as it is termed, or the oxideof iron which coats the surface of the latter. All previous processesfor treating sheet-iron with a view to the manufactures above mentionedhave proceeded upon the supposition that it was necessary to remove thisscale, and various means have been resorted to to effect this purpose,dependin g upon either mechanical or chemical action, or both.

My process does not involve as one of its steps in working it theremoval of the superficial oxide in the sense of separating the scalefrom the sheet, as in the instance where the plates have been cleaned ofscale by the use of mechanical or chemical agents for that purpose; but,on the contrary, I convert the scale into pure iron by depriving it ofthe elements with which the iron combined to form the oxide during theprocess of its manufacture, and at the same time improve the quality ofthe metal of the sheet by driving off any constituent impurities whichit may contain.

I take a convenient number of plates of common sheetiron and pack themin an iron flask of the proper dimensions to accommodate them. The pileof plates is completely covered, as well as their surfaces between eachpair, with turnings or chips of iron. The flask is similar in form tothat used by molders, but is provided with a close-fitting cover, which,after the plates are put inthe box and covered with chips, should bemade at the joint as tight as possible to exclude all air, and this canbe done by smearing the joint with clay. The flask, with its charge ofplates and iron, is then placed in a furnace, which may be of thereverberatory character, or of any other preferred kind which willfurnish a uniform heat of a high temperature. The flask and its contentsare thus heated to a degree which it will be better to have not muchshort of the point which the flask can endure without fusion. I allowthe flask to remain exposed to this heat for a longer or shorter period,depending upon the condition of the furnace and the quality of the ironwhich I am using-upon the average about twelve hours. After the flaskhas become sufficiently cooled it is opened and the plates removed forthe next operation. It will be found that each plate has undergone achange both as to color and quality.

Its surface is of the dull color of unpolished silver, and the scalewill be found to have been reconverted into pure iron, and, in fact, theimpurities which existed in the iron of the body of the sheet will befound to have been in a great degree dissipated as the effect of theprocess of decarhonization which it has undergone. well aware, is thesame as that which has been generally employed in making small castingsmalleable, and therefore I do not claim to have discovered thatcast-iron when subjected to a high heat in a close vessel undergoespurification; but my invention consists in the application of thisprinciple to sheet- V iron plates as an improved means for overcomingthe difficulties due to the presence of scale or other impurities in themanufacture of Russia iron or of plates which are to be coated with zincor other metals. The several plates are next subjected to pressure bybeing passed between the surfaces of polished rollers, the effect ofwhich operation is to render I the two surfaces of the sheet smooth andbright and to roll the films of pure iron which formerly constituted thescale into the perfectly-annealed sheet, so as to exhibit hardly a traceof their ever having existed. The effect of the rollers, however, is toincrease the density of the sheet, and in consequence render it stiff;and as it is desirable, especially if Russia iron is to be manufactured,that the sheet should be perfectly annealed, I deem it advisable torepeat the operation of piling the sheets in a close flask with ironchips and turnings, as before, and expose them again to the heat of thefurnace for a period of twelve hours, more or less, according to theircondition. The sheets, having been allowed to cool This part of myprocess, I amgradually, when taken from the flask will be found to bequite soft and deprived of all elasticity. Their color, more nearly thanbefore, approaches to that of (lull silver, and an examination will showthat the metal is de carbonized throughout. Plates thus prepared are nowready to be blued, if the same are to be finished to imitate Russiairon, by the process described in an application for a patent upon thesubject of manufacturing this variety of iron by me heretofore made, orby any other process which will accomplish the result; and if, insteadof bluing the sheets, it is intended to cover them with a coating ofzinc to produce galvanized iron, or with any other metal, their surfacesare in proper condition to readily take on such coating when dipped inthe bath prepared for that purpose according to the method employed insuch manufacture.

Although my invention is especially adapted to the preparation ofsheet-iron plates for galvanizing, tinning, or otherwise coating themwith metallic substances and for manufacturing Russia iron, it isobvious that the same principle can be successfully employed inpreparing other articlesas, for example, nails and screws-for receivin ga coating of metal to prevent oxidation.

It will be observed that the process which I have described accomplishesnot only the cleaning of the plates on their surfaces, but

improves the quality of the iron of which they are composed, whereas allformer processes with which I am acquainted do not comprehend more thanthe cleaning and smoothing of the surfaces by chemical for mechanicalagents applied to such surfaces.

I do not mean to confine myself to the use of cast-iron chips forcovering the plates while the same are exposed to the action of heat;but I mean to include any equivalent material which can be used for thepurpose, for my invention does not relate to the means by which theresult of decarbonization iszeffected, but to the application of themeans described, or the equivalent chemically thereof, for the purposesdeclared.

What I claim as my invention, and desire to secure by Letters Patent, is

1. Preparing plates of sheet-iron, whether for receiving a coating ofzinc or other metal or preparatory for polishing and coloring inimitation of Russia iron, by the application of the decarbonizin gprocess, substantially as described.

2. Preparing plates of sheet-iron for coloring in imitation of Russiairon by first decarbonizing them and then rolling them, substantially asdescribed.

CHARLES H. PERKINS.

Witnesses JOHN D. THURSTON, GEO. B. BARRoWs.

